utils/sim2.py: build_pcr_tree(): Instead of adding more cycles to complete the tree, just try again. - Add build_good_pcr_tree() which retries if the tree isn't complete.
utils/sim2.py: build_pcr_tree(): Instead of adding more cycles to complete the tree, just try again.
- Add build_good_pcr_tree() which retries if the tree isn't complete.

makrutenko/dunovo,makrutenko/dunovo,makrutenko/dunovo